Sky and Telescope - September 2018 - 6

FROM OUR READERS

Joel Marks
Milford, Connecticut

"

Solace in the Sky
Thank you, Kyle Jeter, for writing
the Focal Point about holding your
Astronomy Night nine days after
the school shooting in Parkland,
Florida (S&T: July 2018, p. 84). I
seldom get tears in my eyes while
reading S&T, but I did while reading
your essay. We cannot see faces at
astronomy events, but the voices
we overhear are probing our place
in the universe. I imagine holding such an event in a community
struck by such horrific violence was
a perfect gift of solace for all who
attended.
Tom Kellogg * San Francisco, California
p Students, parents, and teachers at Marjory Stoneman Douglas High School had
this view of the Moon on their Astronomy
Night on February 23, 2018.

Camille Carlisle replies: Einstein's

S E P TE M B E R 2 018 * SK Y & TELESCOPE

I read with interest the article "The
Little Galaxies That Can" (S&T: Apr.
2018, p. 22) and was intrigued by a
higher primordial helium abundance
(25.5) pointing to a fourth neutrino
type. Would this be the sought-for
sterile neutrino, or would it be an active
type lying beyond the tau?

primordial helium abundance is
higher than predicted and indeed is that way
because there's an additional neutrino
family, it would be a sterile neutrino. It
amazes me that a single percentage point
on helium's abundance could make a
difference between three and four neutrinos!

Home-Grown Globulars

Space Junkie

In "Nearby Relic of Ancient Universe"
(S&T: July 2018, p. 11), Camille Carlisle cites a study of the galaxy NGC
1277, which is "largely ungrown since
the universe's early years." The study's
assumption is that "if NGC 1277 were
really a relic, all its globular clusters
would be rich in heavy elements."
I thought the prevailing wisdom
these days is that early galaxies should
be deficient in heavy elements because
they haven't been synthesized yet by
supernovas. Could you clarify, please?

"Litter in Orbit" (S&T: July 2018, p. 34)
brought back memories. My father and I
had the privilege of observing one of the
first pieces of "space junk" in October
1957. A few days after the launch of
Sputnik 1 by the Soviets, the New York
Daily News printed an article noting
that the booster rocket that carried Sputnik 1 would be crossing the southern sky
of New York City soon after 7:00 p.m.
Dad and I went to our backyard in
Queens and prepared for a glimpse of
the rocket booster. It was dusk, and the
sky was clear. Around 7:15 p.m. Dad
suddenly said, "Look!" and I clearly saw
the booster tumbling end over end from
west to east across the southern sky.

Constant Pressure

6

A Fourth Neutrino?

equations implied that the universe
wasn't static, so it could have been
expanding or shrinking. He interpreted the
result as a shrinking universe due to the
attractive pull of matter's gravity, so he
added a sort of outward "pressure" or
antigravity, which he called lambda, to
counteract gravity and keep everything
balanced. That's why, when he learned of
cosmic expansion, Einstein could forgo the
need for lambda and describe the expansion
with the original equations - and why, when
the antigravity effect of dark energy was
discovered, lambda went back in.

Paul Trent
Yelm, Washington

In his article about dark energy (S&T:
May 2018, p. 14), Marcus Woo notes,
"When applying his theory of general
relativity to cosmology, [Albert] Einstein realized his equations implied the
cosmos doesn't stay still. Presumably,
due to the attractive pull of matter's
gravity, it was shrinking. He deemed
that preposterous. So he introduced a
term, later dubbed the cosmological constant, which represented an antigravity
force that countered the contraction."
But the story as I've always heard

curious: hubblesite.org/news_release/
news/2018-17. At the bottom of that you'll
find a link to the team's paper, too.

Camille Carlisle replies: The globular clusters would be relatively rich
in heavy elements because they've been
around long enough to pollute themselves
as their stars age. Conversely, any globulars
with more pristine compositions would have
been nabbed from smaller satellite galaxies
that NGC 1277 accreted.
So NGC 1277's lack of pristine globulars indicates the galaxy hasn't done much
accreting - its globulars are all homegrown, as it were. Here's a recent press
release that offers more details, if you're

"

Robert Stivers
Edmonds, Washington

"

Camille Carlisle replies: If the

Arthur J. Erdman
Passaic, New Jersey

Retrograde Notion
Did you ever notice how astronomers
name things backward? For example,
when I think about coordinates for the
night sky, I understand that celestial
longitudes increase toward my left as
I face south. Yet we don't call these
longitudes "left ascension" but rather
"right ascension." Similarly, "declina-

K Y LE JE TER

it is that the constant was introduced
in order to "prevent" the universe
from expanding, which is why Hubble's
discovery made Einstein say it had been
his biggest mistake to insert this ad hoc
device in his equations.


http://www.hubblesite.org/news_release/news/2018-17 http://www.hubblesite.org/news_release/news/2018-17

Table of Contents for the Digital Edition of Sky and Telescope - September 2018

Contents
Sky and Telescope - September 2018 - Cover1
Sky and Telescope - September 2018 - Cover2
Sky and Telescope - September 2018 - 1
Sky and Telescope - September 2018 - Contents
Sky and Telescope - September 2018 - 3
Sky and Telescope - September 2018 - 4
Sky and Telescope - September 2018 - 5
Sky and Telescope - September 2018 - 6
Sky and Telescope - September 2018 - 7
Sky and Telescope - September 2018 - 8
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Sky and Telescope - September 2018 - Cover3
Sky and Telescope - September 2018 - Cover4
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